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Adam Levine and Christina Aguilera may argue incessantly over talent on "The Voice," sometimes even nastily.

But if there's one thing the Maroon 5 singer wants the world to know, it's that outside the NBC reality competition, he's got his fellow coach's back, especially from the haters who criticize her over her fluctuating weight.

"People shouldn't say those kinds of things because, f--k you. It's like, come on guys, grow up," Levine, 33, told reporters at a Friday Q&A in New York City when asked about the knocks the 31-year-old songbird has taken over her curvy figure.

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"The one thing about the culture right now--celebrity culture particularly--that is so ugly is [that] people feel like they can just say nasty things about other people...she gets a lot of it," Levine added. "It pisses me off. Of course I have her back, of course I defend her."

The Maroon 5 frontman not only decried the "bullying" the "Your Body" singer has received, but he also took time to address the heated feuds between the two of them on "The Voice," comparing the spats to the kind of fights siblings have.

"The fights that everyone thought we were having were fictional--we never hated each other, we never were having some sort of secret battles that everyone thought we were having," Levine noted. "They were silly bickering things that brother and sister would do. It's not nearly what everybody thought... We're all good, Christina and I."